memblock: Add debug markers at the end of the array

Since we allocate one more than needed, why not do a bit of sanity checking
here to ensure we don't walk past the end of the array ?

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

mm/memblock.c

@@ -13,6 +13,7 @@
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/bitops.h>
+#include <linux/poison.h>
 #include <linux/memblock.h>
 
 struct memblock memblock;
@@ -112,6 +113,10 @@ void __init memblock_init(void)
 	memblock.reserved.regions	= memblock_reserved_init_regions;
 	memblock.reserved.max	= INIT_MEMBLOCK_REGIONS;
 
+	/* Write a marker in the unused last array entry */
+	memblock.memory.regions[INIT_MEMBLOCK_REGIONS].base = (phys_addr_t)RED_INACTIVE;
+	memblock.reserved.regions[INIT_MEMBLOCK_REGIONS].base = (phys_addr_t)RED_INACTIVE;
+
 	/* Create a dummy zero size MEMBLOCK which will get coalesced away later.
 	 * This simplifies the memblock_add() code below...
 	 */
@@ -131,6 +136,12 @@ void __init memblock_analyze(void)
 {
 	int i;
 
+	/* Check marker in the unused last array entry */
+	WARN_ON(memblock_memory_init_regions[INIT_MEMBLOCK_REGIONS].base
+		!= (phys_addr_t)RED_INACTIVE);
+	WARN_ON(memblock_reserved_init_regions[INIT_MEMBLOCK_REGIONS].base
+		!= (phys_addr_t)RED_INACTIVE);
+
 	memblock.memory_size = 0;
 
 	for (i = 0; i < memblock.memory.cnt; i++)